all night; the whole night
Refers to the entire duration of the night, from evening to morning. Often used adverbially with に or without a particle.
It rained all night last night.
He worked the whole night.
Standard kanji spelling. Note that 夜中 can also be read よなか, meaning 'middle of the night', which is a different word.
Mixed kanji-kana spelling that makes the reading unambiguous. Common in everyday writing.
A compound of 夜 “night” and the suffix 中（じゅう） “throughout,” hence “throughout the night.”